docs: def convert(self, destination_units, *, convert_variables=False):
          """Convert axis to destination_units.
  
          Parameters
          ----------
          destination_units : string
              Destination units.
          convert_variables : boolean (optional)
              Toggle conversion of stored arrays. Default is False.
          """
          if self.units is None and (destination_units is None or destination_units == "None"):
              return
          if not wt_units.is_valid_conversion(self.units, destination_units):
              valid = wt_units.get_valid_conversions(self.units)
              raise wt_exceptions.UnitsError(valid, destination_units)
          if convert_variables:
              for v in self.variables:
                  v.convert(destination_units)
          self.units = destination_units